Too much Hytran fluid?
 

Last summer when I restored my 1250, I cleaned out the hydrostat or more so the rear end where all the Hytrans fluid sat for years. But I filled it up to where I thought it was full. I've never really gotten to use the tractor alot due to where I was living...on a small lot in a City. But earlier this spring I bought a house out in the country with an acre to mow....well, last weekend I was rolling the yard and when I was about half way done. The rear end felt like it was grabbing, or like something was binding up. I finished my yard and I put the roller away. I've had a small leak coming from that cork gasket where the hydrostat meets the rearend. So, I thought maybe I was low on Hytrans. So, I remove the plug on the rear end and oil starts barreling out. My question is, is it possible that there could be to much Hytrans oil in the rearend? Could/Will that do any harm?

If you filled it to the filler hole, that would be correct.
When the fluid gets warm, it expands and when taking the plug out when warm, it will seem overfilled.
I would suggest checking again with it is cool.
a dixie cup amount overfilled, isn't going to hurt anything.

I checked it after it had been setting for 3 days....I think its fuller then a dixie cup. I'm going to go home today and take the plug out and let it empty out to the level of the plug.

Did it sit outside at all? I'm wondering if water got into the tranny and raised the level on you. I know hytran encapsulates water, but if enough gets in it will change the level. That could cause the jerkiness too, because water would sink to the bottom where the suction tube picks up.

Also, try to park the tractor on a flat surface for your latest drain/fill attempt. (And cold fluid as noted earlier.)

I have read some post on here where members are removing the plate on top of the transmission and filling it from there. I would be concerned that would overfill the transmission. I always funnel mine in from the drain plug and periodically pull the funnel, waiting for overflow. Once it stops its overflow, then I replug it and run it for a day or two, then let it cool and pull the plug to recheck and/or top off if needed.

Cub Cadet 123

So, I pulled the plug and emptied out what extra was in rear end above the plug line. I went out and mowed this evening and still have the same issue. But what I have noticed is that it only seems to be an issue, the jerkiness as some have put it, is when I am making sharp turns. Could this "jerkiness"/"vibration" possibly be from a worn out wheel bearing on one of the front or rear wheels?

Tractor history
 

Do you know the history of this tractor or is it a "fairly new" acquisition? Just asking, if you don't know the history, you may want to check that the spider gears haven't been welded in the differential.
Jusst a thought Good luck

Old cubby I think I remember resto thread but not sure. Anyway, you didn't mention here that you had changed the filter but only the oil. I'm assuming you changed both but wanted to make sure. If so did you use the correct filter? How bad was original oil? Sounds like it might need oil and filter again if it was bad enough to clog filter. It's hard to get all the bad stuff out in one change, might take multiple times and also some flushing with kerosene or diesel fuel

Jerkiness in a hydro is normally due to cavitation

Yea, This tractor has been in the family since my dad bought it back in 78'. He wasn't much to do any type of work to it unless it was needed, outside of the normal oil changes. It had been sitting beside my dads shed since 99' up until I got it last July and restored it. I am 99.9% sure the spider gears are not welded.

Yes, during restoration I emptied out the Hytrans oil, cleaned out the rear end the best I could....there was alot of greyish color slim stuck around the bottom and sides of the rear end that I cleaned up. When I did this oil change, I used a napa 1410 filter. But as you mentioned.....it could be time to change the oil and filter out again. This is the Hytrans I replaced it with....

Let me know if this is the wrong stuff. I did some looking around and others have used this.

http://www.tractorsupply.com/en/stor...ic-fluid-2-gal